Since a fuel cell system capable of high-efficient and small-scale power generation is conventionally easily configured to use heat energy generated during power generation, it has been developed as a distributed power generation system that is able to achieve high energy utilization efficiency.
The fuel cell system includes a fuel cell which is a power generation portion. In this fuel cell, hydrogen (hydrogen gas) is typically used as a fuel for power generation. However, at present, a hydrogen supply means required to generate power in the fuel cell is not equipped as infrastructure. So, a conventional fuel cell system is equipped with a hydrogen generator configured to generate hydrogen necessary for power generation. In the hydrogen generator, a fossil fuel such as a natural gas is reformed through a predetermined reforming reaction to generate hydrogen. In the conventional fuel cell system, hydrogen generated in the hydrogen generator is supplied to the fuel cell as a fuel for power generation. In the fuel cell, power generation is carried out to output predetermined power using the hydrogen supplied from the hydrogen generator.
In the reforming reaction to generate hydrogen in the hydrogen generator, a steam reforming reaction is typically used. In the steam reforming reaction, the fossil fuel is reformed using the steam to generate hydrogen. So, the water is supplied to the hydrogen generator to generate steam during the power generation operation of the fuel cell system. In order to obtain predetermined power using the fuel cell system, it is essential that a water supply source be obtained in a place where the fuel cell system is installed.
As the water supply means to supply the water to the fuel cell system, a water line is suitably used. When the water line is used as the water supply means, it is necessary to fully remove calcium, chlorine, and so on, from the water supplied from the water line. This is because, if water containing calcium, chlorine, and so on, is supplied to the fuel cell system, performance of the fuel cell system degrades with time due to deposition of calcium or corrosion or the like of a pipe caused by chlorine. So, the conventional fuel cell system is equipped with a water purifier including an ion exchange resin or the like to fully remove calcium, chlorine, and so on, from the water supplied from the water line.
The water purifier including the ion exchange resin or the like is able to fully remove calcium, chlorine, and so on, contained in the water, but a purification ability of the ion exchange resin or the like degrades with time. So, the water purifier including the ion exchange resin or the like must be maintained frequently. This may increase a running cost of the fuel cell system. For this reason, in the conventional fuel cell system, the water is self-supplied in such a manner that water or the like generated by power generation in the fuel cell is obtained by condensation and utilized. In accordance with this water self-supply configuration, a running cost of the fuel cell system can be improved, because the water purifier may be omitted, or a load on the water purifier decreases and thus the frequency of maintenance therefor decreases.
However, the water obtained by condensation in the interior of the fuel cell system does not contain a sterilization component such as chlorine but contains microbes or bacteria, or nutrients, for example, organic matter, necessary for the microbes or the bacteria. For this reason, the water is more likely to decay with time. If decay of the water progresses, then failures such as passage clogging or passage narrowing occurs in a water condenser for condensing the water or in the interior of components such as pipes through which the water is supplied, causing a problem to occur in water supply function.
Accordingly, there have been proposed various means for suppressing progress of decay of water obtained by condensation in the interior of the fuel cell system.
For example, as a means for suppressing progress of decay of water in the interior of the fuel cell system, the components such as the pipes associated with water supply or water condensation, etc, is formed of an antibacterial metal material (see for example, patent document 1).
Also, as a means for suppressing progress of decay of water in the interior of the fuel cell system, an ultraviolet ray is emitted to the water obtained by condensation in the interior of the fuel cell system to kill bacteria, and so on, contained in the water (see for example, patent document 2).
Also, as a means for suppressing progress of decay of water in the interior of the fuel cell system, water flowing in the fuel cell system is controlled to have strong acidity so that the bacteria or the like contained in the water is killed (see for example, patent document 3).
Also, as a means for suppressing progress of decay of water in the interior of the fuel cell system, an antibacterial sterilization filter is provided in a water passage to eliminate bacteria or the like contained in the water (see for example, patent document 4).
Also, as a means for suppressing progress of decay of water in the interior of the fuel cell system, it is detected whether or not water flowing in the interior of the fuel cell system contains microbes, and the ultraviolet ray is emitted to the water if it is detected that the water contains the microbes, to thereby kill the bacteria or the like contained in the water (see for example, patent document 5).
Also, as a means for suppressing progress of decay of water in the interior of the fuel cell system, the temperature of the water flowing in the interior of the fuel cell system is increased up to a predetermined temperature necessary for heating and sterilization (see for example, patent document 6). In this case, to increase the temperature of the water up to the predetermined temperature for heating and sterilization, heat of cooling water that has been increased in temperature and has been discharged from a fuel cell is utilized to reduce an energy necessary to heat the water (see for example, patent document 7).
Patent document 1: Japanese Laid-Open Patent Application Publication No. Hei. 8-22833
Patent document 2: Japanese Laid-Open Patent Application Publication No. Hei. 9-63612
Patent document 3: Japanese Laid-Open Patent Application Publication No. Hei. 9-306523
Patent document 4: Japanese Laid-Open Patent Application Publication No. Hei. 8-63611
Patent document 5: Japanese Laid-Open Patent Application Publication No. 2002-270211
Patent document 6: Japanese Laid-Open Patent Application Publication No. Hei. 8-138714
Patent document 7: Japanese Laid-Open Patent Application Publication No. 2002-270194